Ois: Colin McRea is a 'rally' focused game. TOCA3 has many different styles of racing (thus cars).
Same genre only in that they are 'racing' genres.
captfitz: ah
gog has them both listed as 'racing / simulation / rally'
TOCA 3 defiantly and I'm not even a fan of driving games. I liked it a lot for what it was though, the variation of what was on offer kept me coming back, but its just mindless fun really. Driving games are only as good at the tracks and I found them challenging enough to warrant several repeats.
Colin Mcrae 05 never got interesting enough for me to come back for a second try. I'm no racing veteran, but that's my opinion.